 Solution

For the sequestration hypothesis, ask whether the fragment associates with the proposed alternative partner by co-immunoprecipitation, then compare endogenous complex assembly and cargo localization. An association should be evaluated against empty-vector and inactive-fragment controls, and an independent interaction readout would help distinguish direct binding from membership of a larger complex.

A useful functional test is whether restoring the limiting partner rescues trafficking and invadopodium formation without changing fragment expression or viability. Rescue would support the hypothesis, although overexpression can itself alter trafficking. Binding evidence, the endogenous phenotype and rescue should therefore agree; any one alone is insufficient.